1955-D Lincoln Cent DDR

The arrows are pointing to the MD on the images. The fields are showing the heavy die flow. The image is not mine, but made from several images to give the 3-D effect. But it helps show the differences between die flow (in the fields) and MD (on the devices with arrows). Ray Parkhurst is the one who made these. I use them to show differences on devices. On these two images you can see the die flow and the MD (with arrows) closer up.

I often refer to die wear on the multi-hubbed dies coins. On the Single squeeze die coins I refer to them as a Die Deterioration issue. Why the difference to me?
On the die wear examples the device is altered/enlarged as the die is wearing out.

On the Die Deterioration examples, the area next to the devices on the field is show the deterioration.

This is why I use the different terms. Each is die wear, but they appear different on the two different methods of the dies as they wear. Probably no one else recognizes this, but it is just my own opinion.

MD is movement after the first strike.

The multi-hubbed dies have a taller profile on the devices. The single squeeze dies have a lower profile. So I feel that differences in devices height is the reason. Also the deices are stronger/thinner on the multi-hubbed dies.

Your welcome CC. I never really thought about it either. It's good we continue to learn.
I've been on here long enough to know most of what has been said here and should have looked closer at my coin before posting it. I'm glad I did post it though, because I now know some things I didn't. The biggest thing for me personally, is that Die Wear is not MD. On reflection, I think most people probably pick that up in a month or so. It's referred to a lot on here as MD, and 98% of what I learn is from here. Well, I know it now. The next biggest thing I've learned is the difference between Die Wear and Die Deterioration Doubling and why they are different. I collaterally learned the difference of Die Abrasion Doubling as well. Vertical striation lines can help in identifying Machine Doubling as evidenced in Coop's Atomic Pic. I have also learned that MD is thought to sometimes bounce off of the coin completely thus creating a "second strike". This is not always the case however, and cannot be confirmed on a coin by coin basis. In either case, it is considered to occur during the strike. I base this conclusion on comments like " Mechanical Doubling is a blanket name given to many types of doubling that can happen during the strike." as contained in this thread. Another comment from Mr. Mike Diamond supports the idea it doesn't always lift completely off the coin, can be found in the following link.
http://goccf.com/t/278297
Mr. Diamond is the man the experts ask when they're in doubt. That's a good reason for my position on the matter, a better reason is what he said is very logical. While I do concede the die sometimes separates during the bounce, it is not always the case. Since it can't always be determined, yet one strike is a known, Strike Doubling is considered to occur during the strike and appropriately classified as a mint error. If it was considered to be after the strike, it would be classified as damage.
I strongly dislike having to come back to this, but I feel impressionable Newbies should be able to hear both sides.

Yes always a rotation, but the flattened portion not as high The width varies with the rotation.